Need help with a formula for calculating scores

Question

I need some help figuring out a formula for a school software project I'm working on. I have 2 values, time used and score, what I'm trying to do is to have the final scores be a combination of time used and score, so for the optimal final score, you would have to try to be fast and also get a good score. Top performances will be separated by only a few seconds so I'm trying to have a universal formula that works with most time amounts and score amounts but has a decent size final score difference per second difference. Ideally would like the final score to differ around 10000-20000 pts per second difference. I haven't been able to figure out any way to make it work universally so far. Times will be varying from 50 seconds to 400 seconds and scores from about 100000 to about 1500000. I hope someone smarter in math could help me out, or let me know if what I'm trying is impossible to do with 1 single formula. Thanks!